Vinyl chloride polymer composition

ABSTRACT

A vinyl chloride polymer composition comprising (A) 3 to 50 parts by weight of a grafted copolymer and (B) 97 to 50 parts by weight of a vinyl chloride polymer, a total amount of the copolymer (A) and the polymer (B) being 100 parts by weight; the grafted copolymer (A) comprising 
     (1) 50 to 80 parts by weight of a rubber copolymer and 
     (2) 50 to 20 parts by weight of a grafting monomer, a total amount of the component (1) and the component (2) being 100 parts by weight; 
     the component (1) comprising 
     (a) 60 to 90% by weight of the rubber copolymer comprising 99 to 85% by weight of alkyl acrylate having an alkyl group of 2 to 8 carbon atoms, 1 to 15% by weight of conjugated diolefin and 0 to 5% by weight of polyfunctional cross-linking agent and 
     (b) 40 to 10% by weight of a surface rubber copolymer comprising 98 to 70% by weight of alkyl acrylate having an alkyl group of 2 to 8 carbon atoms, 2 to 30% by weight of conjugated diolefin and 0 to 5% by weight of polyfunctional cross-linking agent and being obtained by polymerizing the component (a) to give a core rubber copolymer and then polymerizing the surface rubber copolymer component (b) in the presence of the core rubber copolymer (a), and a ratio of conjugated diolefin to acrylate in the surface rubber copolymer (b) is larger than a ratio of conjugated diolefin to acrylate in the core rubber copolymer (a) 
     and the component (2) comprising 
     (i) 30 to 95% by weight of methyl methacrylate and 
     (ii) 70 to 5% by weight of at least one monomer selected from the group consisting of unsaturated nitrile, aromatic vinyl compound, alkyl acrylate having an alkyl group of 1 to 8 carbon atoms and alkyl methacrylate having an alkyl group of 2 to 4 carbon atoms. The vinyl chloride polymer composition has excellent impact resistance, weatherability and processability.

BACKGROUND OF THE INVENTION

The present invention relates to a vinyl chloride polymer compositionhaving excellent impact-resistance, weatherability and processability.

It hitherto has been well known that vinyl chloride polymer hasexcellent various properties, but has a disadvantage thatimpact-resistance is poor.

The so-called MBS resin obtained by graft-polymerizing methylmethacrylate, styrene, acrylonitrile, or the like, onto a butadienerubber is widely employed as a reinforcing agent for improving animpact-resistance of vinyl chloride polymer. When MBS resin is employedas a reinforcing agent, an effect of improving the impact-resistance tovinyl chloride polymer is excellent, but double-bond of butadiene unitincluded in a butadiene rubber is readily deteriorated under ultravioletlight, and therefore the weatherability of vinyl chloride polymerbecomes remarkably poor and it is difficult that the vinyl chloridepolymer is practically employed in the outdoors.

In order to eliminate the above disadvantage that the weatherability ispoor, there are proposed various methods that methyl methacrylate,styrene, acrylonitrile, or the like, is graft-polymerized ontocross-linked alkyl acrylate polymer. According to the above methods, theweatherability of vinyl chloride polymer becomes more excellent, but itis unsatisfy to improve the impact-resistance of vinyl chloride polymer.Particularly, the strength of vinyl chloride polymer cannot be increasedwhen vinyl chloride polymer is low-kneaded with the above components.That is to say, the processability of vinyl chloride polymer is poor.The reason why the processability is poor is considered thatcross-linked alkyl acrylate polymer does not have an active site forgrafting, capable of graft-polymerizing onto cross-linked alkyl acrylatewhen the monomers are graft-polymerized onto cross-linked alkylacrylate, unlike the case of MBS resin.

There is also proposed a method employing cross-linkable agents in whichreactivities of functional groups are different. According to the abovemethod, the impact-resistance of vinyl chloride polymer isunsatisfactorily improved.

On the other hand, there are various methods that styrene, methylmethacrylate, acrylonitrile, or the like, is graft-polymerized onto across-linked alkyl acrylate-conjugated diolefin rubber copolymer, inwhich an active site for grafting is provided onto a conjugateddiolefin, as in case of MBS resin. According to the above methods, theimpact-resistance and processability are improved in comparison with amethod employing crosslinked alkyl acrylate polymer as a rubber polymer,but the weatherability tends to become poor, because of existingconjugated diolefin in the rubber copolymer.

And also there is provided a method that the weatherability is not madepoor by employing a rubber polymer, as above-mentioned. In the abovemethod, an alkyl acrylate is copolymerized with a small amount ofconjugated diolefin such that the weatherability is not made poor andthe obtained copolymer is employed as a rubber copolymer. According tothis method, the weatherability is improved, but the impact-resistanceis unsatisfactorily improved. That is to say, as known, an effect ofimproving the impact resistance is increased with increasing a contentof conjugated diolefin in rubber copolymer, but an effect of improvingthe weatherability lowers. On the other hand, an effect of improving theweatherability is increased with decreasing a content of conjugateddiolefin in rubber copolymer, an effect of improving theimpact-resistance lowers.

An object of the present invention is to provide a grafted copolymerhaving an excellent effect of improving the impact-resistance to vinylchloride polymer by employing a small amount of a conjugated diolefin.

A further object of the invention is to provide a vinyl chloride polymercomposition having an excellent impact-resistance, processability andweatherability.

SUMMARY OF THE INVENTION

In the present invention, there is provided a vinyl chloride copolymercomposition comprising 3 to 50 parts by weight (hereinafter referred toas "part") of a grafted copolymer and 97 to 50 parts of a vinyl chloridepolymer, a total amount of the grafted copolymer and vinyl chloridepolymer being 100 parts; the grafted copolymer comprising

50 to 80 parts of a rubber copolymer and

50 to 20 parts of a grafting monomer,

a total amount of the rubber copolymer and the grafting monomer being100 parts;

the rubber copolymer comprising

60 to 90% by weight (hereinafter referred to as "%") of a core rubbercopolymer comprising 99 to 85% of alkyl acrylate having an alkyl groupof 2 to 8 carbon atoms, 1 to 15% of conjugated diolefin and 0 to 5% ofpolyfunctional cross-linking agent and

40 to 10% by weight of a surface rubber copolymer comprising 98 to 70%of alkyl acrylate having an alkyl group of 2 to 8 carbon atoms, 2 to 30%of conjugated diolefin and 0 to 5% of polyfunctional cross-linking agentand being obtained by polymerizing the core rubber copolymer and thenpolymerizing the surface rubber copolymer in the presence of the corerubber copolymer, and a ratio of conjugated diolefin to acrylate in thesurface rubber copolymer is larger than a ratio of conjugated diolefinto acrylate in the core rubber copolymer

and the grafting monomer comprising

30 to 95% of methyl methacrylate and

70 to 5% of at least one monomer selected from the group consisting ofunsaturated nitrile, aromatic vinyl compound, alkyl acrylate having analkyl group of 1 to 8 carbon atoms alkyl group and alkyl methacrylatehaving an alkyl group of 2 to 4 carbon atoms.

DETAILED DESCRIPTION

In the invention, the rubber copolymer is prepared by the two-stagepolymerization so that the core rubber copolymer comprising a smallamount of conjugated diolefin and an alkyl acrylate is first preparedand then the surface rubber copolymer having a high ratio of conjugateddiolefin to the alkyl acrylate in comparison with the ratio of corerubber copolymer is prepared by polymerizing a conjugated diolefin withan alkyl acrylate monomer in the pressure of the core rubber copolymer.The impact-resistance of vinyl chloride polymer employing the rubbercopolymer of the present invention is extremely increased in comparisonwith employing the conventional cross-linkable alkyl acrylate-conjugateddiolefin rubber copolymer having equal amount of conjugated diolefin tothe rubber copolymer of the invention.

In case that the rubber copolymer comprising the core rubber copolymerand the surface rubber copolymer which has a small amount of conjugateddiolefin is employed with vinyl chloride polymer, there can be increasedan impact-resistance the same as in case employing a large amount ofconjugated diolefin, in spite of employing a small amount of conjugateddiolefin, in comparison with the conventional rubber copolymercomprising cross-linkable alkyl acrylate conjugated diolefin.

It is essential that the grafted component graft-polymerized onto therubber copolymer of the invention is compatible with vinyl chloridepolymer from the viewpoint of giving the impact-resistance of vinylchloride polymer. Methyl methacrylate is known as a compatible componentwith vinyl chloride polymer. However, in case that methyl methacrylateis graft-polymerized alone onto the rubber copolymer of the invention,the impact-resistance is not enough, when vinyl chloride polymer islow-kneaded with the obtained grafted copolymer. Accordingly,high-kneading or enough-kneading is necessary to obtain a sufficientimpact-resistance. The necessity of high-kneading or enough-kneadingresults in poor processability. The processability can be extremelyimproved by copolymerizing a small amount of unsaturated nitrile,aromatic vinyl compound, alkyl acryalte, alkyl methacrylate except formethyl methacrylate together with methyl methacrylate. That is to say,when the grafted copolymer of the invention obtained bygraft-polymerizing a grafting monomer component onto the rubbercopolymer of the invention is admixed with vinyl chloride polymer, thevinyl chloride polymer having an excellent impact-resistance is preparedin either case that vinyl chloride polymer is high-kneaded orlow-kneaded with the grafted copolymer.

The rubber copolymer employed in the present invention is prepared in ausual emulution-polymerization by employing an alkyl acrylate having analkyl group of 2 to 8 carbon atoms and a conjugated diolefin, and asoccasion demands, a polyfunctional cross-linking agent to give a corerubber copolymer, and then in further polymerization to give a surfacerubber copolymer.

The alkyl group which forms alkyl acrylate having an alkyl group of 2 to8 carbon atoms, in the invention, may be a linear or branched one.Examples of the alkyl acrylate are, for instance, ethyl acrylate, propylacrylate, n-butyl acrylate, isobutyl acrylate, pentyl acrylate, hexylacrylate, n-octyl acrylate, 2-ethylhexyl acrylate, and the like. Thesemonomers can be employed alone or in the admixture thereof.

Typical examples of the conjugated diolefin monomer to be copolymerizedwith alkyl acrylate are, for instance, 1,3-butadiene, isoprene, and thelike. These monomers can be employed alone or in the admixture thereof.

In the invention, as afore-mentioned, it is necessary that the rubbercopolymer is prepared by at least two-stage polymerization, that is tosay, the core rubber polymer is first prepared by polymerization andthen the surface rubber copolymer is obtained by polymerization in thepresence of the above core rubber copolymer. And further, it isnecessary that a ratio of conjugated diolefin to alkyl acrylate in thesurface rubber copolymer is higher than that in the core rubbercopolymer. The core rubber copolymer comprises 99 to 85%, preferably 99to 90% of the above alkyl acrylate and 1 to 15%, preferably 1 to 10% ofconjugated diolefin, and as occasion demands, 0 to 5% of polyfunctionalcross-linking agent. The monomer components in the surface rubbercopolymer to be polymerized onto the core rubber copolymer are 98 to70%, preferably 94 to 70% of alkyl acrylate and 2 to 30%, preferably 6to 30% of conjugated diolefin, and as occasion demands, 0 to 5% ofpolyfunctional cross-linking agent. A ratio of diolefin to alkylacrylater in the surface rubber copolymer of more than 30 % is notpreferable from the viewpoint of an effect of improving theweatherability. And further, a ratio of diolefin to alkyl acryalte inthe surface rubber copolymer of less than 2% is not preferable from theviewpoint of an effect of improving the impact-resistance. This thing isassumed as is decreasing active site for grafting. On the other hand, itis preferable that a ratio of conjugated diolefin to alkyl acrylate inthe surface rubber copolymer is larger than a ratio of conjugateddiolefin to alkyl acryalte in the core rubber copolymer from theviewpoint of an effect of improving the impact-resistance. It ispreferable to more than 3%, more preferably more than 5%. In case that aratio of conjugated diolefin to alkyl acrylate in the surface rubbercopolymer is less than a ratio of conjugated diolefin to alkyl acrylatein the core rubber copolymer, it is not practical since an effect ofimproving the impact-resistance lowers.

The rubber copolymer of the invention is prepared by polymerizing 60 to90%, preferably 70 to 90% of core rubber copolymer and 40 to 10%,preferably 30 to 10% of surface rubber copolymer. In case that an amountof the surface rubber copolymer is less than 10%, it is not preferablesince an effect of improving the impact-resistance lowers. On the otherhand, in case that the above amount is more than 40%, it is notpreferable since the weatherability tends to lower.

It is necessary that the grafting monomers of the invention, which arepolymerized onto the rubber copolymer, are enough selected. It isimportant that the grafting monomers are compatible with vinyl chloridepolymer from the viewpoint of getting an effect of improving theimpact-resistance. Methyl methacrylate is well-known as a typicalexample of the component being compatible with vinyl chloride polymer.

In case that only methyl methacrylate is graftpolymerized onto therubber copolymer to give the grafted copolymer, a vinyl chloride polymerhaving a satisfactory impact-resistance is obtained by means ofhigh-kneading, such as roll-processing, of the grafted copolymer andvinyl chloride polymer. However, when the grafted copolymer islow-kneaded, such as pipe-processing with vinyl chloride polymer, it isvery difficult that the obtained vinyl chloride polymer is employed forpractical use, because it is difficult that the thus obtained graftedcopolymer gives an effect of improving the impact-resistance to vinylchloride polymer. In the invention, it is essential to employ methylmethacrylate for getting the impact-resistance to vinyl chloridepolymer. On the other hand, it is necessary that at least one of monomerselected from the group consisting of unsaturated nitrile, aromaticvinyl compound, alkyl acrylate and alkyl methacrylate except for methylmethacrylate is copolymerized together with methyl methacrylate forfurther increasing an effect of improving the impact-resistance in casethat vinyl chloride polymer is low-kneaded with the grafted-copolymer.

In the invention, a grafting monomer component to be graft-polymerizedonto the rubber copolymer comprises 30 to 95%, preferably 40 to 90% ofmethyl methacrylate and 5 to 70%, preferably 10 to 60% of at least onemonomer selected from the group consisting of unsaturated nitrile,aromatic vinyl compound, alkyl acrylate having an alkyl group of 1 to 8carbon atoms and alkyl methacrylate having an alkyl group of 2 to 4carbon atoms. In case that an amount of methyl methacrylate amonggrafting monomers is less than 30%, it is not preferable because oflowering of the effect of improving the impact-resistance. On the otherhand, the above amount of methyl methacrylate is more than 95%, it isnot preferable that the effect of giving the impact-resistance is alittle.

Typical examples of the above aromatic vinyl compound is styrene, andthe others are vinyl toluene and α-methyl styrene. Examples of theunsaturated nitrile are, for instance, acrylonitrile, methacrylonitrile,and the like. Examples of the alkyl acrylate are, for instance, ethylacrylate, methyl acrylate, n-butyl acrylate, and the like. Examples ofthe alkyl methacrylate are, for instance, ethyl methacrylate, n-butylmethacrylate, and the like.

A monomer selected from the group consisting of styrene, acrylonitrile,ethyl methacrylate, n-butyl methacrylate and n-butyl acrylate isextremely preferable as a monomer component to be copolymerized togetherwith methyl methacrylate. An effect for improving the strength intovinyl chloride polymer becomes high by employing the above monomer whenvinyl chloride polymer is low-kneaded without impairing an excellentcompatibility to vinyl chloride polymer, which is given by employingmethyl methacrylate.

On the other hand, as components capable of giving an excellentcompatibility to vinyl chloride polymer, various components such asaromatic vinyl compound and unsaturated nitrile copolymer other thanmethyl methacrylate compolymer have been known. The various methods areproposed to improve the processability of vinyl chloride polymer byskillfully combining the above component giving an excellentcomparibility and methyl methacrylate or selecting an order adding tovinyl chloride polymer when the components are polymerized.

When those known graft-polymerization method is employed for the rubbercopolymer of the invention, it is preferable since the processability ofvinyl chloride polymer is improved and the excellent property of therubber copolymer appears. For instance, it is preferable tograft-polymerize a monomer mixture comprising 30 to 95% of methylmethacrylate and 5 to 70% of at least one monomer selected from thegroup consisting of unsaturated nitrile, aromatic vinyl compound, alkylacrylate having an alkyl group of 1 to 8 carbon atoms and alkylmethacrylate having an alkyl group of 2 to 4 carbon atoms onto therubber copolymer without changing any kind of components of monomermixture. And further, it is more preferable that a monomer mixtureincluding not less than 30% of methyl methacrylate is copolymerized atthe finishing stage of copolymerization from the viewpoint of effects ofimproving the processability and impact-resistance.

That is to say, in the graft-polymerization method of the graftedcopolymer of the invention, 5 to 30 parts, preferably 10 to 25 parts ofa monomer mixture comprising 50 to 90%, preferably 60 to 80% of aromaticvinyl compound and 10 to 50%, preferably 20 to 40% of unsaturatednitrile, 0 to 40%, preferably 0 to 20% of alkyl methacrylate having analkyl group of 1 to 4 carbon atoms and 0 to 40%, preferably 0 to 20% ofalkyl acrylate having an alkyl group of 1 to 8 carbon atoms is firstgraft-polymerized onto 50 to 80 parts, preferably 60 to 75 parts of therubber copolymer; and then 5 to 30 parts, preferably 10 to 25 parts of amonomer mixture comprising 30 to 95%, preferably 40 to 90% of methylmethacrylate and 5 to 70%, preferably 10 to 60% of at least one monomerselected from the group consisting of unsaturated nitrile, aromaticvinyl compound, alkyl acrylate having an alkyl group of 1 to 8 carbonatoms and alkyl methacrylate having an alkyl group of 2 to 4 carbonatoms is secondly graft-polymerized to give the grafted copolymer. Atotal amount of the rubber copolymer, the first graft-polymerizedmonomer mixture and the second graft-polymerized monomer mixture is 100parts. On the other hand, 5 to 30 parts, preferably 10 to 25 parts of amonomer mixture comprising 30 to 95%, preferably 40 to 90% of methylmethacrylate and 5 to 70%, preferably 10 to 60% of at least one monomerselected from the group consisting of unsaturated nitrile, aromaticvinyl compound, alkyl acrylate having an alkyl group of 1 to 8 carbonatoms and alkyl methacrylate having an alkyl group of 2 to 4 carbonatoms is first graft-polymerized onto 50 to 80 parts, preferably 60 to75 parts of the rubber copolymer; and then 5 to 30 parts, preferably 10to 25 parts of a monomer mixture comprising 50 to 90%, preferably 60 to80% of aromatic vinyl compound, 10 to 50%, preferably 20 to 40% ofunsaturated nitrile, 0 to 40%, preferably 0 to 20% of alkyl methacrylatehaving an alkyl group of 1 to 4 carbon atoms and 0 to 40%, preferably 0to 20% of alkyl acrylate having an alkyl group of 1 to 8 carbon atoms issecondly graft-polymerized to give the grafted copolymer. A total amountof the rubber copolymer, the first graft-polymerized monomer mixture andthe second graft-polymerized monomer mixture is 100 parts. In case thatthe grafted copolymer obtained by above-mentioned polymerization methodis kneaded with vinyl chloride polymer, it is more preferable since theimpact-resistance is extremely improved and excellent properties of therubber copolymer appear, even if the grafted copolymer is low-kneadedwith vinyl chloride polymer as in pipe-processing.

The grafted copolymer is prepared by graft-polymerization with 50 to 20parts, preferably 40 to 25 parts of grafting monomer onto 50 to 80parts, preferably 60 to 75 pats of the rubber copolymer. A total amountof the rubber copolymer and grafting monomers is 100 parts. In case thatan amount of the rubber copolymer is less than 50 parts, it is notpractical that the effect of improving the impact-resistance is poor. Onthe other hand, in case that an amount of the rubber copolymer is morethan 80 parts, it is difficult that the rubber copolymer is uniformlykneaded with vinyl chloride polymer because the rubber copolymer isaggregated at the time of salting-out, aciding-out or drying theprepared grafted copolymer.

The thus obtained grafted copolymer latex is subjected to salting-out oraciding-out, and filtration, washing and drying to give the graftedcopolymer. In the time of depositing, a conventional antioxidant orultraviolet absorbent may be added.

The obtained grafted copolymer is kneaded with vinyl chloride polymer togive the viny chloride polymer compositon of the invention. "Vinylchloride polymer" in the instant specification is included vinylchloride homopolymer, vinyl chloride copolymer having not less than 70%of vinyl chloride and the derivatives thereof such as chlorinatedpolyvinyl chloride.

An amount of the grafted copolymer to vinyl chloride polymer isdifferent depending upon the use. In general, the amount is 3 to 50parts of the grafted copolymer to 97 to 50 parts of vinyl chloridepolymer.

The present invention is more specifically described and explained bymeans of the following Examples. It is to be understood that the presentinvention is not limited to Examples, and various changes andmodifications may be made in the invention without departing from thespirit and scope thereof.

EXAMPLE 1 (A) Preparation of a core rubber copolymer

After a space in stainless reactor was thoroughly displaced withnitrogen gas, the reactor was charged with the following components andthe polymerization was carried out at 40° C. for 10 hours.

Deionized water: 250 parts

n-Butyl acrylate: 94 parts

Butadiene: 6 parts

p-Menthane hydroperoxide: 0.05 part

Sodium formaldehyde sulfoxylate: 0.05 part

Di-sodium salt of ethylenediamine-tetrahydroacetic acid (hereinafterreferred to as "Di-sodium salt of EDTA"): 0.003 part

Ferrous sulfate (FeSO₄.7H₂ O): 0.0015 part

Tri-potassium phosphate: 0.4 part

Sodium oleate: 2.5 parts.

At five hours after the beginning of polymerization, 0.03 part ofp-menthanehydroperoxide was added to the polymerization mixture. Aconversion of the obtained latex was 96% and an average particlediameter was 1000Å.

(B) Preparation of a rubber copolymer

After a space in autoclave was thoroughly displaced with nitrogen gas,the autoclave was charged with the following components and thepolymerization was carried out at 40° C. for 6 hours.

Deionized water: 250 parts

The core rubber copolymer obtained in (A): 80 parts

n-Butyl acrylate: 16.8 parts

Butadiene: 3.2 parts

p-Menthane hydroperoxide: 0.003 part

Sodium formaldehyde sulfoxylate: 0.03 part

Di-sodium salt of EDTA: 0.003 part

Ferrous sulfate (FeSO₄.7H₂ O): 0.0015 part

Tri-potassium phosphate: 0.1 part.

There was added 1% aqueous solution including 0.75 part of sodium oleatefor 3 hours from the beginning of the polymerization. At 5 hours afterthe begining of the polymerization, 0.03 part of p-menthanehydroperoxide was added to the polymerization mixture. A conversion ofthe obtained latex was 96% and average an particle diameter was 1100Å.

(C) Preparation of a grafted copolymer

Rubber copolymer latex obtained in (B): 65 parts (solid)

Deionized water: 200 parts

Sodium formaldehyde sulfoxylate: 0.4 part

Di-sodium salt of EDTA: 0.01 part

Ferrous sulfate (FeSO₄.7H₂ O): 0.005 part.

A reactor was charged with the above-mentioned components and a space inreactor was thoroughly displaced with nitrogen gas while maintaining at60° C. After adding 0.13 part of hydrogen chloride (as 0.33% aqueoushydrochloric acid solution) to the solution, 2% sodium hydroxidesolution was added to the mixture to make stable. An average particlediameter of the rubber copolymer latex was 1600Å.

And then the following components were added to the obtained latex for 4hours and further the polymerization was carried out for 1 hour. Aconversion of the grafted copolymer latex was 97%.

Methyl methacrylate: 25 parts

Styrene: 8 parts

Acrylonitrile: 2 parts

Cumene hydroperoxide: 0.3 part.

There was added 0.5 part of 2,4-dimethyl-6-t-butylphenol into theobtained grafted copolymer latex, and salting-out was carried out.Thereafter, the latex was dehydrated and dried to give the desiredgrafted copolymer.

The obtained grafted copolymer was mixed with vinyl chloride polymer andother additives according to Formulation 1 and the obtained compositionwas molded into a vinyl chloride polymer pipe having a diameter of oneinch by employing a biaxial extruder having a diameter of 80 mm.

A falling impact-strength of the obtained pipe was measured by means ofthe following method.

The results are shown in Table 1.

And further, the obtained composition was roll-kneaded for 5 minutes at160° C. and compression-molded for 15 minutes by employing a heat-pressof 180° C. according to Formulation 2 to prepare a sample for Izotimpact test. Then, the sample was treated with a weather-o-meter andIzot impact-strength of the sample was measured by means of thefollowing method.

The results are shown in Table 1.

[Formulation 1]

Vinyl chloride polymer (P=1,000): 100 parts

Grafted copolymer: 7 parts

Lead stabilizer: 2 parts

Calcium stearate: 1 part

Wax lubricant: 0.5 part

[Formulation 2]

Vinyl chloride polymer (P=1,000): 100 parts

Grafted copolymer: 13 parts

Dibutyltinmercaptide: 2 parts

Epoxidized soybean oil: 1 part

Wax lubricant: 0.5 parts

(Falling impact strength)

A mean-broken height of one inch pipe is measured at 0° C. by employinga weight having a flat bottom.

(Izot impact-strength)

After carrying out a weathering test of the obtained sample by employinga sunshine-weather-o-meter (made by Toyo Seiki Kabushiki Kaisha) under acondition of a black-panel temperature of 63° C. and a rainfall of 12minutes per 2 hours Izot impact-strength is measured at 23° C. accordingto JIS K 7110.

EXAMPLES 2 and 3 and COMPARATIVE EXAMPLES 1 to 3

The procedure of Example 1 was repeated except that ratios of the corerubber copolymer and the surface rubber copolymer in the rubbercopolymer and each ratio of n-butyl acrylate and butadiene in the corerubber copolymer or the surface rubber copolymer were changed as shownin Table 1 to give grafted copolymers. And then, the obtained copolymerswere admixed with vinyl chloride polymer to prepare samples. Physicalproperties of the obtained samples were measured.

The results are shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________    Rubber copolymer                                                              Ratio of conjugated diolefin    Ratio of conjugated diolefin                  to acrylate in the core                                                                         Ratio of the core                                                                           to acrylate in the surface                    rubber copolymer (%)                                                                            rubber copolymer in the                                                                     rubber copolymer (%)                              BA.sup.(1)                                                                           BD.sup.(2)                                                                           rubber copolymer (%)                                                                        BA.sup.(1)                                                                           BD.sup.(2)                             __________________________________________________________________________    Ex. 1                                                                             94     6      80            84     16                                     Ex. 2                                                                             96     4      80            76     24                                     Ex. 3                                                                             93     7      80            88     12                                     Com.                                                                              92     8      100           --     --                                     Ex. 1                                                                         Com.                                                                              92     8      80            92      8                                     Ex. 2                                                                         Com.                                                                              91     9      80            96      4                                     Ex. 3                                                                         __________________________________________________________________________    Physical properties                                                                                         Izot impact-strength (kgcm/cm.sup.2)            Ratio of the surface                                                                          Falling cone impact strength                                                                0  100                                                                              200 300                                                                              400                                rubber copolymer in the                                                                       (cm) (Mean-broken height of                                                                 (Irradiation time of sunshine                   rubber copolymer (%)                                                                          one inch pipe)                                                                              weather-o-meter(hr.))                           __________________________________________________________________________    Ex. 1                                                                             20          250           90 80 70  50 30                                 Ex. 2                                                                             20          270           130                                                                              90 65  40 20                                 Ex. 3                                                                             20          220           -- -- --  -- --                                 Com.                                                                              --          150           50 40 30  25 15                                 Ex. 1                                                                         Com.                                                                              20          170           -- -- --  -- --                                 Ex. 2                                                                         Com.                                                                              20          160           -- -- --  -- --                                 Ex. 3                                                                         __________________________________________________________________________     .sup.(1) BA: nButyl acrylate                                                  .sup.(2) BD: Butadiene                                                   

EXAMPLE 4

The rubber copolymer latex obtained in Example 1: 65 parts (solid)

Deionized water: 200 parts

Sodium formaldehyde sulfoxylate: 0.4 part

Di-sodium salt of EDTA: 0.01 part

Ferrous sulfate (FeSO₄.7H₂ O): 0.005 part

A reactor was charged with the above components. An aggregation andstabilization of the components were carried out in the same manner asin Example 1. Thereto the following components were added for 2 hoursand further the polymerization was carried out for 1 hour. A conversionof the grafted copolymer was 96%.

Methyl methacryalte: 14 parts

Styrene: 4 parts

Acrylonitrile: 2 parts Cumene hydroperoxide: 0.2 part.

Thereto there were added the following components for 2 hours and thepolymerization was carried out for 1 hour. An conversion of the obtainedgrafted copolymer was 98%.

Methyl methacryalte: 13 parts

n-Butyl acrylate: 2 parts

Cumene hydroperoxide: 0.2 part.

The obtained grafted copolymer was molded into a vinyl chloride polymerpipe having a diameter of one inch in the same manner as in Example 1and a falling impact-strength was measured.

EXAMPLES 5 to 7 and COMPARATIVE EXAMPLE 4

The procedure of Example 4 was repeated except that the graftingmonomers shown in Table 2 were employed. The obtained grafted copolymerwere kneaded with vinyl chloride polymer, and the samples of vinylchloride polymer compositions were prepared and the physical propertieswere measured.

The results are shown in Table 2.

                                      TABLE 2                                     __________________________________________________________________________                                         Falling impact-                          Grafting monomers in the                                                                        Grafting monomers in the                                                                         strength (cm)                            first polymerization (part)                                                                     second polymerization (part)                                                                     (Mean-broken height                      MMA.sup.(1)                                                                            ST.sup.(2)                                                                        AN.sup.(3)                                                                         MMA.sup.(1)                                                                        ST.sup.(2)                                                                       AN.sup.(3)                                                                        BA.sup.(4)                                                                       BMA.sup.(5)                                                                       of one inch pipe)                        __________________________________________________________________________    Ex. 1                                                                             25   8   2    --   -- --  -- --  250                                      Ex. 4                                                                             14   4   2    13   -- --  2  --  260                                      Ex. 5                                                                             --   11  4    18   -- --  2  --  270                                      Ex. 6                                                                             18   2   --   --   11 4   -- --  230                                      Ex. 7                                                                             --   11  4    16   -- --  -- 4   250                                      Com.                                                                              35   --  --   --   -- --  -- --  130                                      Ex. 4                                                                         __________________________________________________________________________     .sup.(1) MMA: Methyl methacrylate                                             .sup.(2) ST: Styrene                                                          .sup.(3) AN: Acrylonitrile                                                    .sup.(4) BA: nButyl acrylate                                                  .sup.(5) BMA: nButyl methacrylate                                        

What we claim is:
 1. A vinyl chloride polymer composition comprising(A)3 to 50 parts by weight of a grafted copolymer and (B) 97 to 50 parts byweight of a vinyl chloride polymer, a total amount of said copolymer (A)and said polymer (B) being 100 parts by weight;said grafted copolymer(A) comprising (1) 50 to 80 parts by weight of a rubber copolymer and(2) 50 to 20 parts by weight of a grafting monomer, graft polymerizedonto said component (1) a total amount of said component (1) and saidcomponent (2) being 100 parts by weight;said component (1) comprising(a) 60 to 90% by weight of a core rubber copolymer comprising 99 to 85%by weight of alkyl acrylate having an alkyl group of 2 to 8 carbonatoms, 1 to 15% by weight of conjugated diolefin and 0 to 5% by weightof polyfunctional cross-linking agent and (b) 40 to 10% by weight of asurface rubber copolymer comprising 98 to 70% by weight of alkylacrylate having an alkyl group of 2 to 8 carbon atoms, 2 to 30% byweight of conjugated diolefin and 0 to 5% by weight of polyfunctionalcross-linking agent and being obtained by polymerizing said component(a) to give a core rubber copolymer and then polymerizing said surfacerubber copolymer component (b) in the presence of said core rubbercopolymer (a), and a ratio of conjugated diolefin to acrylate in saidsurface rubber copolymer (b) is larger than a ratio of conjugateddiolefin to acrylate in said core rubber copolymer (a)and said component(2) comprising (i) 30 to 95% by weight of methyl methacrylate and (ii)70 to 5% by weight of at least one monomer selected from the groupconsisting of unsaturated nitrile, aromatic vinyl compound, alkylacrylate having an alkyl group of 1 to 8 carbon atoms and alkylmethacrylate having an alkyl group of 2 to 4 cabron atoms.
 2. The vinylchloride polymer composition of claim 1, wherein said ratio ofconjugated diolefin to acrylate in said surface rubber copolymer (b) ismore than 3% of ratio of conjugated diolefin to acrylate in said corerubber copolymer (a).